Students can be undeleted from the Audit log. Any data associated to that student will be restored in School Reporting mode and in Reports in Teacher mode.
1.1 In Admin Mode, select the "More" tab on the home page.
1.2 Select a student by checking the box before its name.
1.3 Select "Undelete" from the toolbar.
1.4 After undeleting the student, Restored will show in the Action column.